Spamassassin is a memory killer. OTOH, it only comes to action when an email is received (as per default, things may be different when you tweaked your installation). You have 512K for 90 users, which is rather low. How much messages do you get per hour on average?

When no mail is being received, there should not be any spamassassin process. Might be worth to investigate why there are so many processes left. You also have 10 zombies ("dead" processes). Could those be those spamassassin ones?

You might try to get rid of these by stopping starting ISPConfig, but I'm afraid you'll have to reboot the server. Watch the swap space being used. As soon as that happens your system will slow down significantly.

Something is completely clogging your system. And it's very IO intensive (look at wait time, that's waiting for disks data to be returned to the requesting program). Also, you now have even 37 zombies. That's worse then before. What's the output of

That's an adminstrative email to count the used bandwith/bytes for email. These are really small emails and should not be of much problem. I'm still wondering why ISPConfig does not follow the default of SA to skip large emails.

In the top directory of you web (/var/www/web1 or something), there is a file called .procmailrc. It describes which tests to include for mails to that domain. Comment the spamassassin line. Mind that ISPConfig overwrites this file when you change a mail setting of the user.

An even better idea pops up now that I type this: You can reset the tickbox in ISPConfig for the user mail. (Spam and Antivirus). You can disable SA very easy this way, even per user.

I'm trying all but the server go slowly.
I have a lot of mail in postfix queue like 300...delete all queue could be a good solutions?
Could be a hardware problem? (Stopping postfix all seem to work fast)
Reinstall Ispconfig could help?

If you can afford to delete your mail queue (e.g your users will not go mad, because you delete legitimate mail), that might help. Otherwise, let it process and in quite hours your system will catch up.

Anyway, consider a memory upgrade, if possible.

A re-install of ISPConfig will not help at all. That would be a waste of resources (time and effort).